The present invention relates generally to a fluid pressure energy translating device of the vane type that is suitable for applications such as pumping water in space applications and employs water as the lubricating fluid.
The design of a vane pump for pumping fresh water in space applications presents a serious challenge to the designer because of requirements of light weight and infrequent maintenance. Also, when pumping water it is desirable for the pump to be self-lubricating, i.e., to use the pumped fluid itself as a lubricant. The poor lubricity and low viscosity of water compared with lubricating oils contributes to the challenge. The low viscosity dictates that all design clearances must be an order of magnitude less than for oil lubricated devices. In addition, the potential contamination of scarce water in a space vehicle requires that no oils or greases be used. A high pumping efficiency is clearly advantageous, since a given pumping rate is achievable with the minimum expenditure of power.
Generally, vane devices comprise a circular rotor disposed within a non circular cam ring, so that the gap between the rotor and the cam ring varies according to the angular position within the ring. Vanes are disposed in openings around the periphery of the rotor, and when in motion, make sliding contact with the inside of the cam ring. The vanes are free to move back and forth in the openings, being urged into continuous contact with the cam ring by centrifugal force, springs or hydraulic pressure. As the vanes move around the cam ring, they displace fluid into zones of increasing volume, causing more fluid to enter from an inlet port, or into zones of decreasing volume, from which fluid is discharged through an outlet port.
Various examples of vane pumps have been disclosed previously. While various examples of pumps perform satisfactorily for their intended purposes, certain limitations prevent them from performing satisfactorily as water pumps in space environments. In particular, space applications demand that pump weight be minimized and that the pump provide efficient trouble-free operation for extremely long periods with minimal maintenance.
The invention disclosed herein describes a bi-directional, self-lubricating vane-type water pump. The pump comprises a rotor with a plurality of radial slots, each of which accommodates a vane. The rotor and vanes are driven by a drive shaft to revolve within a non-circular cam ring, displacing fluid and causing it to enter through an inlet port, or to be discharged through an outlet port, the ports being present in port plates. In this invention, the port plates and the cam ring are disposed in a highly symmetrical fashion, which promotes efficiency and furthermore provides equally efficient operation of the pump in either direction. Within narrow prescribed limits, the drive shaft of the pump is free to float back and forth along its axis. This axial movement may be controlled through a shim washer placed at the end the drive shaft. This provides optimum efficiency, permitting sufficient clearance between components to avoid binding and allow the pumping fluid, for example water, to lubricate where required, but nevertheless preventing excessive play. The fluid flows in the pump are subject to minimal constriction, which also contributes to efficient operation. Additionally, wear resistant and friction resistant materials may be employed for specific component parts, so as to obviate the need for conventional bearings. The pump requires very little maintenance, and is suitable for installation in remote locations such as space.
Accordingly, it is an object of this invention to provide an improved pump for fluids of low viscosity which has an extremely long operating lifetime with minimal maintenance and is suitable for space applications.
It is further an object of this invention to provide an improved pump for fluids of low viscosity which has a simple design, such that fluid flows are minimally constricted, providing optimal efficiency.
It is further an object of this invention to provide an improved bi-directional pump for fluids of low viscosity which has a high internal symmetry, allowing effectively equal efficiency in either direction.
It is further an object of this invention to provide a pump requiring minimal maintenance via the elimination of dynamic seals.
Finally, it is an object of this invention to provide an improved pump for fluids of low viscosity which is self lubricating.